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Sam, nestled within the Alibori Department of Benin, occupies a geographically significant position in the northern savanna region of the country. Located at approximately 11.0333° N, 2.7333° E, the city’s terrain is characterized by gently undulating plains, typical of the Sahelian landscape. The surrounding area is predominantly agricultural, with extensive millet, sorghum, and maize cultivation dominating the rural landscape. This proximity to agricultural zones introduces a potential source of particulate matter, particularly during harvesting and burning seasons. The urban–rural gradient around Sam is relatively gradual, with small villages and agricultural fields transitioning seamlessly into the city’s periphery. While Sam lacks immediate proximity to major rivers or lakes, it benefits from seasonal rainfall patterns that sustain agricultural productivity. The elevation is relatively low, averaging around 250 meters above sea level, which can contribute to temperature inversions during the dry season, trapping pollutants closer to the ground. The city’s regional position, far from major industrial belts, initially suggests lower industrial pollution. However, the increasing use of biomass fuels (wood and charcoal) for cooking and heating, coupled with vehicular traffic, represents a localized pollution challenge. The prevailing winds, generally from the north during the dry season, can transport dust and pollutants from surrounding agricultural areas and potentially from further afield across the Sahel, impacting air quality within Sam. The landscape is largely open, offering some natural ventilation, but the increasing population density is altering this dynamic.

Sam’s tropical savanna climate dictates a distinct wet and dry season cycle, profoundly influencing its air quality. The dry season, typically spanning from November to March, presents the most significant air quality challenges. Reduced rainfall leads to lower atmospheric moisture, promoting dust generation from agricultural fields and unpaved roads. Temperature inversions are more frequent during this period, trapping pollutants near the ground, particularly during cooler nights. The reliance on biomass fuels for cooking and heating intensifies during the dry season as temperatures drop, releasing significant quantities of particulate matter and carbon monoxide. Agricultural burning practices, common during land preparation, further exacerbate the problem. The months of January and February often experience the poorest air quality due to a combination of these factors. Conversely, the wet season (April to October) brings relief. Frequent rainfall effectively washes pollutants from the atmosphere, and higher humidity reduces dust generation. Wind patterns shift, often bringing moist air from the south, dispersing any accumulated pollutants. While the wet season generally offers improved air quality, periods of intense rainfall can lead to localized flooding and the release of mould spores, potentially affecting respiratory health. Sensitive groups, including children, the elderly, and individuals with pre-existing respiratory conditions, should exercise caution during the dry season, limiting outdoor activities during peak pollution periods and ensuring adequate ventilation in homes. During the wet season, vigilance regarding mould exposure is advised.